The invention relates to a thermostat valve for a cooling system of an internal-combustion engine.
Thermostat valves are used for controlling the coolant temperature in the cooling circuit of an internal-combustion engine. In conventional cooling circuits, there is a so-called small cooling circuit, where the coolant is guided through the engine but not through the radiator of a vehicle, and a large cooling circuit, where the flow takes place through the engine as well as through the radiator, in which case, the coolant releases the heat absorbed from the engine back into the radiator. In order to open and close the flow connections between the sections of the cooling circuit, the thermostat valve has a temperature-sensitive thermostat element that lifts and lowers a valve disk, which opens or closes a radiator-side coolant inlet.
FIG. 1 illustrates a conventional thermostat valve 10 having a thermostat housing 12, in which an engine-side coolant inlet 14 and a radiator-side coolant inlet 16 are provided, which are disposed opposite one another. In addition, a laterally arranged coolant outlet 18 leading to the engine is provided in the thermostat housing 12. A thermostat element 20, which defines a longitudinal axis A, is oriented in an essentially centered fashion with respect to the coolant inlets 14, 16 in the thermostat housing 12. A valve disk 22 is fixedly connected with the thermostat element 20 and can close and open the radiator-side coolant inlet 16, in that it rests on a valve seat 24 or is released from the latter. In addition, a second valve disk 26 is fixedly connected with the thermostat element 20, which can open or close the engine-side coolant inlet 14.
At low coolant temperatures, the radiator-side coolant inlet 16 will be closed, while the engine-side coolant inlet 14 is open, so that the flow takes place only through the small coolant circuit. When the thermostat element 20 expands as the temperature rises, the two valve disks 22, 26 will be displaced in the upward direction in the FIG. 1. With a rising temperature, the engine-side coolant inlet 14 will therefore be closed, while the radiator-side coolant inlet 16 is opened in order to switch from the small coolant circuit to the large cooling circuit.
Due to component tolerances of the valve disk 22 and/or of the valve seat 24, there often is a slight undesired tilting of the valve disk 22 or of the valve seat 24. In a borderline case, this may have the result that, in a first stroke range of the valve disk 22, during the opening of the radiator-side coolant inlet 16, a gap 28 is already created in an unintended manner between the valve disk 22 and the valve seat 24, through which cold coolant from the radiator flows into the thermostat valve 10 and flows around the thermostat element 20 before it flows off through the engine-side outlet of the thermostat valve 10. In this borderline case illustrated in FIG. 1, as a result of the component tolerances, the valve disk 22 has a maximal tilt of an angle αT with respect to a plane perpendicular to the longitudinal axis A, the valve disk 22 being oriented in the thermostat housing 12 such that the angle αT and therefore the resulting gap 28 between the valve disk 22 and its valve seat 24 is opened toward the wall of the thermostat housing 12 and away from the coolant outlet 18.
In this case, the temperature reaction of the thermostat valve 10 is falsified because the coolant flowing back from the engine, which essentially is to define the control temperature, is displaced or mixed with cold coolant. Based on the resulting cold coolant flow around the thermostat element 20, the switching temperature of the thermostat valve 10 shifts upward by the amount ΔT (see FIG. 2b). The coolant temperature at the thermostat element 20 is therefore lower than the temperature of the coolant flowing back from the engine, so that the actual switching point at the thermostat valve 10 may be at an undesirably high temperature.
For the purpose of comparison, the temperature difference is illustrated in FIGS. 2a and 2b. FIG. 2a shows a characteristic temperature-time line to switching point S of the thermostat valve 10 for an ideally oriented valve disk 22 (αT=0). In contrast, FIG. 2b illustrates the situation shown in FIG. 1, in which the maximal component tolerance, thus a maximally large angle αT as well as a tilt of the valve disk 22 in the direction of the wall of the thermostat housing 12 are combined. The deviation ΔT may amount to up to 5° C.
It is therefore an object of the invention to reduce variation between the inlet temperature of the coolant into the engine and the switching temperature of the thermostat valve.
According to the invention, a thermostat valve for a cooling system of an internal-combustion engine includes a thermostat housing having an engine-side and a radiator-side coolant inlet, which are disposed opposite one another. The thermostat valve further includes a lateral coolant outlet leading to the internal-combustion engine, and a valve disk, which has an end face, which interacts with a valve seat of the radiator-side coolant inlet and is disposed opposite the valve seat. The valve disk is disposed between the radiator-side coolant inlet and a thermostat element arranged in the thermostat housing. A switching direction of the valve disk defines a longitudinal axis. The valve disk has a disk part and a guiding element connected with the latter at the outer edge of the disk part. The guiding element has a deflecting surface on the exterior side, which prevents the thermostat element from a direct or too excessive cold flow towards the thermostat element. A greater mixing of the radiator-side, relatively cold coolant with engine-side, relatively warm coolant can thereby be achieved before the mixed coolant contacts with the thermostat element, which can minimize a contact of unmixed cold coolant with the thermostat element and thus minimize undesirable variation of the switching temperature of the thermostat valve.
The deflecting surface may extend away from the end face to the engine-side coolant inlet and, in addition, away from the longitudinal axis, whereby the coolant flowing in out of the radiator-side coolant inlet is guided laterally away from the longitudinal axis of the thermostat element. According to a preferred embodiment, the guiding element is designed as a closed circumferential collar. The collar may be a funnel which widens to form a free edge. As a result, regardless of the actual angular position of the tolerance, which causes tilt of the valve seat and/or of the valve disk, cold coolant can be guided away from the thermostat element. However, in an alternative embodiment, the collar may be provided only in sections on the circumference of the valve disk and thereby exercise a shielding effect.
In another aspect of the invention, optionally an acceleration of the flow of the relatively cold coolant out of the radiator-side coolant outlet can be achieved with respect to the relatively warm coolant out of the engine-side coolant outlet, in order to ensure a good mixing, before the mixed water can flow to the thermostat element.
The guiding element may, in addition, have a cross-section which widens in the direction of the engine-side coolant inlet, whereby a mixing of coolant from both coolant inlets is further promoted.
Preferably, an exterior lateral surface of the guiding element is constructed as at least one part of the deflecting surface. In an embodiment, the disk part and/or the guiding element can also be connected with one another in one piece.
According to a further embodiment, the deflecting surface adjoins the outer edge of the disk part and, in an area spaced away from the disk part in the direction of the longitudinal axis, has a diameter which amounts to more than 110%, preferably at least 125%, of the outside diameter of the disk part. This ensures the lateral deflection of the coolant.
In an embodiment, the thermostat element extends from the disk part essentially in the direction of the longitudinal axis to the engine-side coolant inlet.
According to a further embodiment, an angular tolerance of the valve seat and/or of the assigned end face is provided at the valve disk relative to a plane perpendicular to the longitudinal axis. At any angle within the angular tolerance, preferably also in any rotational position of the angle about the longitudinal axis, a radially outermost point of the deflecting surface is farther away from the longitudinal axis than a radially inside radius of the valve seat. As a result, it is ensured that the radiator-side coolant, before it contacts with the thermostat element, is first laterally deflected therefrom. As a result of the flow conditions in the thermostat housing, a greater mixing of coolant from the two inlets can therefore be ensured, particularly when the angular tolerance is designed such that the radiator-side coolant first flows into the valve on the side facing away from the coolant outlet.
This advantage can also be achieved or increased in that, in addition or as an alternative, the deflecting surface is rotationally symmetrical with respect to a center axis extending perpendicularly to the end face and expands from the disk part to a radially outermost point of the deflecting surface on average by an angle with respect to the center axis, which preferably is by multiple times greater than the angular tolerance, in which case, in a radially sectional view, the deflecting surface has a straight, stepped and/or curved shape.
According to a preferred further embodiment, the valve disk extends in the direction of the longitudinal axis along at least a quarter, preferably at least a third or at least half of the distance between the engine-side and the radiator-side coolant inlet, whereby the guiding of the radiator coolant to the engine coolant flow is improved.
It may further be provided that, at least in a circumferential area facing away from the coolant outlet, the valve disk has an outside diameter that corresponds essentially to an inside diameter of the thermostat housing, whereby the valve disk rests almost on the interior side of the thermostat housing, whereby, at least in this circumferential area, the radiator-side coolant is maximally laterally guided away from the thermostat element.
Preferably, the disk part, the guiding element and/or the valve disk consist of an identical material and, in particular, are connected with one another in one piece and/or are produced as a workpiece, which may be advantageous in view of the manufacturing and the mounting of these parts.
The thermostat valve is preferably designed in a known manner such that it can allow or prevent a coolant flow through the radiator-side coolant inlet of the internal-combustion engine, and also such that it can allow or prevent a coolant flow through the engine-side coolant inlet. According to a known construction, a second valve disk may be provided in the thermostat valve, which is also fixedly connected with the thermostat element, and which can close and open the engine-side coolant inlet, in order to control the switching of the large and the small coolant circuit.
The thermostat element may be arranged in a conventional manner on the longitudinal axis. In this case, the valve disk is preferably fixedly connected with the thermostat element. In this manner, the tolerance compensation has the greatest possible effect.
According to the invention, several of the above-described further developments of the invention can also—if technically conceivable—be combined with one another.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.